Hydraulic control system for controlling line pressure based on backtorque and throttle rate in an automatic transmission

Abstract

An automatic transmission includes a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements. A hydraulic control system selectively supplies a hydraulic pressure to the friction coupling elements, thereby selectively applying the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern. The control system sets a target hydraulic pressure to be applied to the friction coupling elements according to the kind of the shift to be effected and the engine load, and, when it is detected that the transmission gear mechanism is to make a backout upshift due to reduction in the engine load, increases the target hydraulic pressure by an amount which is determined according to the throttle opening and the turbine speed.

What is claimed is: 
     
       1. A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:   wherein said rotational speed detecting means detects the rotational speed of a turbine of a torque convertor as the rotational speed of the driving system, and said correction means determines the amount by which the target hydraulic pressure set by the target hydraulic pressure setting means is increased according to the kind of the back torque upshift as well as to said parameter indicative of the engine load and the rotational speed of the driving system.   
     
     
       2. A hydraulic control system as defined in claim 1 in which said back torque shifts are divided into a plurality of kinds by the friction coupling element to be applied in the back torque shift. 
     
     
       3. A hydraulic control system as defined in claim 2 in which said back torque shifts are divided into a two kinds, one consisting of the back torque upshifts in which a 2-4 brake is applied and the other consisting of the back torque shifts in which a 3-4 clutch is applied. 
     
     
       4. A hydraulic control system as defined in claim 2 in which said back torque shifts are divided into a plurality of kinds by the gear speed to which the transmission gear mechanism is to shift. 
     
     
       5. A hydraulic control system as defined in claim 4 in which said back torque upshifts are divided into three kinds, one consisting of the backout upshifts in which the transmission gear mechanism shifts to second, another consisting of the back torque upshifts in which the transmission gear mechanism shifts to third and the other consisting of the back torque upshifts in which the transmission gear mechanism shifts to fourth. 
     
     
       6. A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:   wherein said correction means determines the amount by which the target hydraulic pressure set by the target hydraulic pressure setting means is increased according to the kind of the back torque upshift as well as to the said parameter indicative of the engine load and the rotational speed of the driving system.   
     
     
       7. A hydraulic control system as defined in claim 6 in which said back torque shifts are divided into a plurality of kinds by the friction coupling element to be applied in the back torque shift. 
     
     
       8. A hydraulic control system as defined in claim 7 in which said back torque shifts are divided into two kinds, one consisting of the back torque upshifts in which a 2-4 brake is applied and the other consisting of the back torque shifts in which a 3-4 clutch is applied. 
     
     
       9. A hydraulic control system as defined in claim 7 in which said back torque shifts are divided into a plurality of kinds by the gear speed to which the transmission gear mechanism is to shift. 
     
     
       10. A hydraulic control system as defined in claim 9 in which said back torque upshifts are divided into three kinds, one consisting of the back torque upshifts in which the transmission gear mechanism shifts to second, another consisting of the back torque upshifts in which the transmission gear mechanism shifts to third and the other consisting of the back torque upshifts in which the transmission gear mechanism shifts to fourth. 
     
     
       11. A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:   wherein said rotational speed detecting means detects the rotational speed of a turbine of a torque convertor as the rotational speed of the driving system and said correction means increases the target hydraulic pressure only when the engine load is in a predetermined range.   
     
     
       12. A hydraulic control system as defined in claim 11 in which said back torque shifts are divided into a plurality of kinds by the friction coupling element to be applied in the back torque shift. 
     
     
       13. A hydraulic control system as defined in claim 12 in which said back torque shifts are divided into two kinds, one consisting of the back torque upshifts in which a 2-4 brake is applied and the other consisting of the back torque shifts in which a 3-4 clutch is applied. 
     
     
       14. A hydraulic control system as defined in claim 12 in which said back torque shifts are divided into a plurality of kinds by the gear speed to which the transmission gear mechanism is to shift. 
     
     
       15. A hydraulic control system as defined in claim 14 in which said back torque upshifts are divided into three kinds, one consisting of the back torque upshifts in which the transmission gear mechanism shifts to second, another consisting of the back torque upshifts in which the transmission gear mechanism shifts to third and the other consisting of the back torque upshifts in which the transmission gear mechanism shifts to fourth. 
     
     
       16. A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:   wherein said correction means increases the target hydraulic pressure only when the engine load is in a predetermined range.   
     
     
       17. A hydraulic control system as defined in claim 16 in which said back torque shifts are divided into a plurality of kinds by the friction coupling element to be applied in the back torque shift. 
     
     
       18. A hydraulic control system as defined in claim 17 in which said back torque shifts are divided into two kinds, one consisting of the back torque upshifts in which a 2-4 brake is applied and the other consisting of the back torque shifts in which a 3-4 clutch is applied. 
     
     
       19. A hydraulic control system as defined in claim 17 in which said back torque shifts are divided into a plurality of kinds by the gear speed to which the transmission gear mechanism is to shift. 
     
     
       20. A hydraulic control system as defined in claim 19 in which said back torque upshifts are divided into three kinds, one consisting of the back torque upshifts in which the transmission gear mechanism shifts to second, another consisting of the back torque upshifts in which the transmission gear mechanism shifts to third and the other consisting of the back torque upshifts in which the transmission gear mechanism shifts to fourth. 
     
     
       21. A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and a degree of opening of a throttle valve for an engine throttle valve detecting means which detects a parameter indicative of the degree of opening of the throttle valve and another parameter indicative of the rate of change in the degree of opening of the throttle valve, a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in of said another parameter indicative of the rate of change in the degree of opening of the throttle valve the degree of opening of the throttle valve at a rate not less than a predetermined rate, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means which, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the degree of opening of the throttle valve and the rotational speed of the driving system, and does not correct the target hydraulic pressure when the back torque upshift is not detected.   
     
     
       22. A hydraulic control system as defined in claim 21 in which said shifts are divided into a plurality of kinds by the friction coupling element to be applied in the shift. 
     
     
       23. A hydraulic control system as defined in claim 22 in which said upshifts are divided into two kinds, one consisting of the upshifts in which a 2-4 brake is applied and the other consisting of the shifts in which a 3-4 clutch is applied. 
     
     
       24. A hydraulic control system as defined in claim 22 in which said shifts are divided into a plurality of kinds by the gear speed to which the transmission gear mechanism is to shift. 
     
     
       25. A hydraulic control system as defined in claim 24 in which said upshifts are divided into three kinds, one consisting of the upshifts in which the transmission gear mechanism shifts to second, another consisting of the upshifts in which the transmission gear mechanism shifts to third and the other consisting of the upshifts in which the transmission gear mechanism shifts to fourth.